Method and device for positioning patients with breast cancer in prone position for imaging and radiotherapy

ABSTRACT

A method and device for accurately easily and accurately positioning patients with breast cancer in the prone position for imaging and radiotherapy is disclosed. The device is a couch or support structure with a double-layer structure that allows relative planar motion between the two layers. To easily slide the top layer, an array of ball transfer units is embedded on the upper side of the bottom layer while the under side of the top layer has a corresponding array of bearing plates to prevent the ball transfer units from grinding into the top layer. A locking mechanism is specially designed to interlock the two layers safely when a knob handle is tightened. A frame of bars is attached to the bottom layer to constrain translation of the top layer. Each layer has two openings for the through insertion of breasts. When a patient lies in the prone position, the breast to be treated is pendent through the couch, and the untreated breast may be blocked from radiation exposure by a removable opening cover.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to radiotherapy equipment and,more particularly, to a method and device for positioning patients withbreast cancer in the prone position for imaging and radiationtreatments.

2. Description of the Background

Breast cancer has become a global concern with over one million newcases reported annually. In the United States alone, the National CancerInstitute estimates that there will be about 200,000 new cases of breastcancer in 2009. Approximately twenty percent of these cases will resultin fatalities.

Radiation therapy is an established method of treating patients withbreast cancer especially when patients choose to conserve their breasts.When irradiating a breast, patient position bears an emerging concern.Currently most patients with breast cancer are treated in the supine(lying on the back) position, while the most sensitive and specificMagnetic Resonance Imaging (MRI) is performed in the prone (face down)position. Radiation treatment in the supine position only allows accessfrom a few angles, and the supine position is also inferior due to thegravitational force, compressing the breast against the chest (which iscompounded with large-breasted patients). In addition, breast motionresulting from breathing creates inaccuracies in locating the beamwithin the target volume.

Realizing the limitations of the supine position, imaging and treatingpatients with breast cancer from the prone position has been suggestedby many researchers and physicians. With a patient lying on a patientsupport device or couch in the prone position, imaging or radiationtherapy is implemented with the patient's breast pendent through anopening in the support device or couch. In the prone position, thebreast tissue is pulled away from the chest wall by the gravitationalforce, which allows more access to the breast and reduces radiationexposure to the critical organs in the thorax (e.g., lung and heart).Another benefit of the breast radiation treatment in the prone positionis that tumor targeting is more accurate by reducing the target motionassociated with cardiac systole and respiratory movement. Manyresearchers have demonstrated that treating breast cancer by setting thepatient in the prone position is more advantageous than in theconventional supine position.

One of the major issues of placing a patient in the prone position isthat, once lying in the prone position, the patient losses the abilityto move controllable distances for accurate positioning of her breast,especially when the patient is weak or overweight. When irradiating atumor, it is very important to target it precisely. Unfortunately, dueto difficulties in setting up patients in the prone position, bothbreast cancer screening and radiotherapy are more often performed in thesupine position than in the prone position, although it more preferableto image and treat the breast in the prone position.

A number of patient positioning methods and devices have been developedin the past. U.S. Patent Application No. 20070036267 disclosed a patientpositioning device to reduce skin radiation exposure when irradiatingbreast cancer in the prone position. The device employs a gas-filledbladder to spare the skin from receiving high radiation dose. U.S.Patent Application No. 19975609152 proposed a patient-supporting tablefor performing stereotactic mammographic biopsy procedures in the proneposition. The table can pendently present a patient's breast in twodifferent orientations with respect to the aperture. In U.S. PatentApplication No. 20080201850, Brito et al. designed a patient positioningplatform that allows a patient to lie in the prone position duringbreast imaging. The platform has a cushioned base to support thepatient's torso and articulate head and arm rests. U.S. PatentApplication No. 20070033735 provided a method and device for accuratelyand reproducibly positioning a patient's breast to receive radiationwhile the patient is in the prone position upon a radiation treatmenttable. The treatment table includes a generally flat patient supportsurface and a head positioning device. U.S. Pat. No. 5,564,438 proposeda method and apparatus for prone position radiation therapy of breasttissue. The apparatus effectively isolates the breast tissue to beirradiated from the rest of the body. U.S. Patent Application No.20090064413 provided a patient support system to be used with a standardlinear accelerator for prone position breast radiotherapy. The systemallows access of the treatment beam to the breast from up to 360degrees. U.S. Patent Application No. 20006047420 shows a head and upperbody support system comprising three distinct supports. Each support hasan inclined lower portion to support and lift the patient's abdomen andan upper portion to support the corresponding shoulder and the upperbody. U.S. Patent Application No. 20056922859 proposed a patientpositioning table for a medical procedure on a breast. The surface ofthe table can be adjusted to fit the shape of the patient's body. U.S.Patent Application No. 20080043905 disclosed a portable pronestereotactic mammography system for biopsies, image guided lumpectomies,and radiation treatment of breast. The system allows a physician toperform prone breast operations at any desired location. U.S. PatentApplication No. 20026367104 disclosed a patient support method andapparatus for obtaining mammographic images. Using this method, thepatient is placed in a left or right lateral decubitus position topresent her breast to a mammography device. There are also commerciallyavailable prone breast boards or couches for facilitating breasttreatments in the prone position. However, all these methods and devicescannot alleviate the difficulties in accurate patient positioning, whichmotivates the present invention, e.g., a novel method and device forprecisely positioning patients with breast cancer in the prone positionfor imaging and radiation treatments.

The present invention allows easy and accurate patient setup in theprone position by using a double-layer couch with the top layer floatingover the bottom layer for easily adjusting the position of the patient.

SUMMARY OF THE DISCLOSURE

It is the primary objective of the present disclosure to provide amethod and device to allow easy and accurate patient setup in the proneposition for breast imaging using computed tomography (CT), MRI, andradiation treatments.

It is another objective to provide a method and device as describedabove that includes a mechanism to facilitate easy movement of a patientin the prone position so that the patient and the patient's breast canbe precisely positioned along two horizontal axes.

It is another objective to provide a method and device in the form of acouch including a thick bottom layer for strength and a thin top layerthat interfaces with the patient, and a mechanism to allow the top layerof the couch to make planar movements easily and efficiently relative tothe bottom layer of the couch.

It is another objective to provide a method and device as describedabove that includes a mechanism to interlock the two layers convenientlyand safely.

It is another objective to provide a method and device as describedabove that includes a mechanism to block the untreated breast fromreceiving unnecessary radiation exposure.

It is another objective to provide a method and device as describedabove that includes a mechanism to constrain the motion range of the toplayer of the couch.

In accordance with the foregoing objects, the present disclosuredescribes a radio-imaging couch comprising a thick bottom layer forstrength and a thin top layer that interfaces with the patient, and amechanism to allow the top layer of the couch to make planar movementseasily and efficiently relative to the bottom layer of the couch. In anillustrative embodiment, the translation mechanism uses ball transferunits to facilitate the easy sliding motion between the top and bottomlayers. More specifically, an array of hard bearing plates (titanium orother non-ferromagnetic material providing a hard surface) is embeddedin the underside of the top layer, and an array of ball transfer unitsis embedded in the upper side of the bottom layer. The balls of the balltransfer units face up to support the top layer. For MRI imaging, suchball transfer units may employ ceramic balls and non-ferromagnetic metalhousing(s). The hard bearing plates on the top layer of the couchprevent the balls of the ball transfer units from grinding into the toplayer.

With the help of the ball transfer units, the top layer is able to slideon the bottom layer easily and reliably. In addition, there is a lockingmechanism that interlocks the two layers safely. When the top layer isunlocked, an attendant can slide it conveniently through the lockingmechanism. However, a frame of bars is attached to the bottom layer tolimit sliding, and prevent the top layer from sliding away. Each layerof the couch has two openings for a breast to go through the couch, anda cover is provided to block one of the openings, allowing only one ofthe breasts to be pendent through the couch. The couch is preferablyequipped with a comfortable pad on its top surface, and the couch isadapted for positioning patients in the prone position.

BRIEF DESCRIPTION OF THE FIGURES

Other objects, features, and advantages of the present invention willbecome more apparent from the following detailed description of thepreferred embodiments and certain modifications thereof when takentogether with the accompanying drawings in which:

FIG. 1 is a schematic illustration of a breast cancer patient positionedon the disclosed imaging/treatment couch with a breast pendent throughan opening of the couch;

FIG. 2 is an illustration of the double-layer couch allowing the toplayer to easily slide on the bottom layer;

FIG. 3 is a cross section of the double-layer couch showing the balltransfer units and the hard bearing plates;

FIG. 4 is a cross section of the double-layer couch showing the lockingmechanism;

FIG. 5 is a detailed view of the under side of the top layer showing thehard bearing plates; and

FIG. 6 is detailed view of the upper side of the bottom layer showingthe embedded ball transfer units.

DETAILED DESCRIPTION

The present disclosure is a method and device for accurate positioningof patients in the prone position for breast imaging and treatment.Using the disclosed new device, one can adjust the position of a patientin the prone position easily and accurately.

Referring to FIG. 1, the patient 2 is positioned on a couch 1 comprisinga top layer 4 and a bottom layer 8 (here obscured). The patient'stargeted breast is pendent through an opening of the couch 1. Note thata thin mattress or pad may be put between the patient and the top of thecouch for the patient's comfort.

A schematic design of the double-layer couch is illustrated in FIG. 2,including the top layer 4 and the bottom layer 8. Different materialscan be used for the top and bottom layers 4, 8. For MRI imaging, thematerials used for both layers should be non-ferromagnetic so that thecouch will not distort the magnetic field in the imaging space. For thepurpose of illustration, and as one example of the embodiment, plasticmay be used for both the top and bottom layers 4, 8. The couch 1 shouldbe strong enough to hold the patient 2. For this purpose, both the topand bottom layers should have a certain thickness. For the purpose ofillustration, and as one example of an embodiment, the bottom layer 8 ofthe couch 1 is thicker for added strength while the top layer 4 isthinner to facilitate patient translation relative to the bottom layer.

For easy relative motion between the top and bottom layers 4, 8, afriction reduction medium is preferably used to separate the two layers.The friction reduction medium may include, but is not limited to, fluidmediums such as pressured air, lubricants, and low friction coatings onthe bottom surface of the top layer or on the upper surface of thebottom layer, or various mechanical roller elements such as balls orrollers. For the purpose of illustration, and as one example of theembodiment, the embodiment disclosed herein employs an array of balltransfer units for achieving such low friction relative motion.

With ball transfer units, the patient's weight rests on the balls of theball transfer units. To prevent the balls of the ball transfer unitsfrom cutting into the surface they roll on, the surface that the ballsroll on must be very hard. As described in detail below, this may beaccomplished with an array of hard plates 9 attached on the bottom sideof the top layer 4 at locations corresponding to the ball transfer unitsembedded in the bottom layer.

FIG. 3 is a cross section of the double-layer couch 1 showing anexemplary ball transfer unit 10 embedded in top surface of the bottomlayer 8, and a corresponding hard bearing plate 9 embedded in the bottomsurface of the top layer 4. The hard bearing plate 9 may comprisetitanium.

FIG. 5 is a detailed view of the underside of the top layer 4 showingthe embedded hard bearing plates 9. As best seen in FIG. 5, the toplayer 4 has an array of hard bearing plates 9 on its under side. Eachbearing plate 9 is a substantially flat plate that provides adownwardly-facing bearing surface. The top layer 4 is also defined bytwo openings 13. The two openings 13 are uniform, and the cover 6 isinterchangeable so as to selectively occlude either opening 13. In thisway, cover 6 allows only one breast of the patient 2 to extend pendentthrough the opening 13 allowing the breast to be drawn by the force ofgravity away from the patient's chest. Additionally, two smalldistally-positioned holes 12 on the top layer 4 are used by the lockingmechanism as shown in FIG. 4.

Now referring to FIG. 6, the bottom layer 8 has an array of balltransfer units 10, each corresponding to one of the array of bearingplates 9 on the top layer 4. The bottom layer 8 also provides twoopenings 16 (corresponding to openings 13 in the top layer 4) allowingthe patient's breast to pendently extended. Two step holes 18 on thebottom layer 8 are used by the locking mechanism as shown in FIG. 4. Thebottom layer 8 is preferably slightly larger than the top layer 4.

With collective reference to FIGS. 3 and 6, in an embodiment, each balltransfer unit 10 is radiation-transparent and further comprises asingle-rolling-element bearing including, for example, a ceramic ball 22held captive in a titanium or other non-ferromagnetic material housing24. The ball 22 protrudes from the face of the housing 24 to provide anupwardly-facing bearing point upon which the bearing plate 9 in the toplayer 4 contacts. The ball 22 is rotationally seated within the housing24 and maintains a slight separation between the top layer 4 and bottomlayer 8. The combined array of ball transfer units 10 (FIG. 6) andopposing bearing plates 9 (FIG. 5) allow the top layer 4 to slide on thebottom layer 8 easily and reliably.

FIG. 2 shows an exemplary embodiment in which a frame of peripheralrestraining bars 7 is connected to the bottom layer 8. The top layer 4is slidably inserted into the frame 7 to prevent the top layer 4 fromsliding beyond the periphery of the restraining bars 7. In this example,the top layer 4 is smaller than the bottom layer 8, which leaves a gapbetween the periphery of the top layer 4 and the periphery ofrestraining bars 7. In this illustration, a cover strip 5 is provided tocover this gap, thereby improving aesthetics and sanitary conditions.

In use, the targeted breast is placed through an opening 13 or 16 in therespective top and bottom layers 4, 8, while the other breast is placedabove the couch's top layer 4 supported by the cover 6. Thisconfiguration protects the untreated breast from unnecessary radiationexposure.

The couch 1 preferably has a locking mechanism to fix the relativepositions of the top and bottom layers 4, 8. The locking mechanism shownin FIG. 4 interlocks the two layers 4, 8 safely. When the top layer 4 isunlocked, an attendant can slide it freely. When the top layer 4 islocked, the translational motion of the top layer 4 is constrained. Thelocking mechanism may be accomplished by a number of types ofconstraints including a pin protruding from one layer into a hole with aconforming diameter within the other layer, or an upwardly or downwardlyprotruding frame on either layer to keep the opposing layer captive, orby attaching interlocking bars or pins to the circumference of the topor bottom layer. One skilled in the art should understand that othersuitable means may exist to achieve this locking purpose.

FIG. 4 shows one embodiment in which the two layers 4, 8 are lockedtogether by a friction brake. In this example, the locking mechanismcomprises a knob handle 3 that is accessible from above the top layer 4turns in an integral threaded stud 26. The knob handle 3 and stud 26pass down through both the top and bottom layers 4, 8. The threaded stud26 engages a brake pad 11 lying beneath the bottom layer 8.Specifically, in this embodiment the knob handle 3 includes a hub thatis seated in and traverses an unthreaded hole 12 on the top layer 4. Thethreaded stud 26 of the knob handle 3 engages a threaded hole on thebrake pad 11. The brake pad 11 is embedded in the step hole 15 on thebottom layer 8 as seen in FIG. 6. This way, when the knob handle 3 istightened, the brake pad 11 is pulled inward into contact with thebottom layer 8. When the knob handle 3 is fully tightened, the top layer4 becomes locked to the bottom layer 8 due to the friction between thebrake pad 11 and the bottom layer 8.

The couch 1 preferably also includes a mechanism that can be used tomove the top layer 4 around conveniently and easily relative to thebottom layer 8. Any of a variety of knobs, pins, handgrips, or othersuitable means may achieve this purpose. For the purpose ofillustration, and as one example of the embodiment, the knob handle 3 ofthe locking mechanism may be used to move the top layer 4. When threadedstud 26 is disengaged with the threaded hole on the brake pad 11, thebrake pad 11 is no longer in contact with the bottom layer 8. As aresult, the locking friction between the brake pad 11 and the bottomlayer 8 is eliminated. Thus, the top layer 4 may slide on the bottomlayer 8 freely by moving applying force to the knob handle 3. Note thatthe knob handle 3 should be closely fit the hole 12 on the top layer 4,and the brake pad 11 should be smaller than the step hole 15.

A detailed view of the bearing plates 9 and the ball transfer units 10are shown in FIG. 3. The ball transfer units 10 are installed such thattheir apices have the same height and are higher than the top side ofthe bottom layer 8. The bearing plates 9 may be embedded in conformingpockets formed on the underside of the top layer 4. The dimensions arecalculated to leave a small gap between the top layer 4 and the bottomlayer 8 separated by the balls 22 of the ball transfer units. Thebearing plates 9 slide on the apices of the ball transfer units 10 toprevent the apices from cutting into the top layer 4. Although theillustrated embodiment has the ball transfer units 10 attached to thebottom layer 8 and the bearing plates 9 attached to the top layer 4,this orientation may be reversed—the ball transfer units 10 may beattached to the top layer 4, and the bearing plates 9 may be attached tothe bottom layer 8.

It should now be apparent that the above-described device allows easyand accurate patient setup in the prone position for breast imaging andtreatment, including easy movement and stabilization of a patient sothat the patient and the patient's breast can be precisely positionedalong two horizontal axes.

It is recognized that various modifications are possible within thescope of the claimed invention. Thus, it should be understood that,although the present invention has been specifically disclosed in thecontext of preferred embodiments and optional features, those skilled inthe art may resort to modifications and variations of the conceptsdisclosed herein. Such modifications and variations are considered to bewithin the scope of the invention as defined by the appended claims.

1. A multi-layer couch for accurately positioning patients with breastcancer in the prone position for radio imaging, comprising: a top layerhaving a top surface for supporting a patient in the prone position, abottom surface, and a pair holes; a bottom layer having a top surfaceand a pair of holes; a friction reduction mechanism between said toplayer and said bottom layer for minimizing friction there between; andwherein said pair of holes in the top layer and said pair of holes inthe bottom layer are adjacently aligned for insertion of a patient'sbreast.
 2. The multi-layer couch for accurately positioning patientswith breast cancer in the prone position for radio imaging according toclaim 1, wherein said friction reduction mechanism further comprises aplurality of ball transfer units attached to said top layer or saidbottom layer.
 3. The multi-layer couch for accurately positioningpatients with breast cancer in the prone position for radio imagingaccording to claim 2, wherein said plurality of ball transfer units areattached to the top surface of said bottom layer.
 4. The multi-layercouch for accurately positioning patients with breast cancer in theprone position for radio imaging according to claim 2, furthercomprising a plurality of bearing plates attached to the other layer ofsaid top layer or said bottom layer to which said ball transfer unitsare attached.
 5. The multi-layer couch for accurately positioningpatients with breast cancer in the prone position for radio imagingaccording to claim 1, further comprising a locking mechanism forselectively locking said top layer to said bottom layer to preventrelative translation.
 6. The multi-layer couch for accuratelypositioning patients with breast cancer in the prone position for radioimaging according to claim 5, wherein said locking mechanism comprises ascrew-tightened friction brake.
 7. The multi-layer couch for accuratelypositioning patients with breast cancer in the prone position for radioimaging according to claim 1, further comprising a translation limitingmechanism for limiting relative translation of said top layer to saidbottom layer.
 8. The multi-layer couch for accurately positioningpatients with breast cancer in the prone position for radio imagingaccording to claim 6, wherein said translation limiting mechanismcomprises a frame of bars surrounding said bottom layer to limitrelative translation of the top layer.
 9. The multi-layer couch foraccurately positioning patients with breast cancer in the prone positionfor radio imaging according to claim 1, further comprising a removablecover for selectively covering one of said pair of holes in the toplayer to prevent insertion of a patient's breast.
 10. A method foraccurately positioning patients with breast cancer in the prone positionfor radio imaging, comprising the steps of: lying said patient on amulti-layer couch in the prone position, said multi-layer couchcomprising a first layer and a second layer, said patient placing abreast through a hole through the first and second layers of said couch;adjusting said first layer of said couch relative to said second layerof said couch by relative translation between said layers; and lockingsaid first layer of said couch in position relative to said second layerof said couch to prevent relative translation between said layers.
 11. Adouble-layer support platform for positioning patients with breastcancer in the prone position for imaging and radiotherapy, comprising atop layer for patient-support slidably mounted on a bottom layer forrelative translation, said top layer being defined by two adjacentopenings for insertion of a patient's breast, and said bottom layerbeing defined by two adjacent openings corresponding to said openings inthe top layer.
 12. The double-layer support platform for positioningpatients according to claim 11, wherein said top layer is separated fromsaid bottom layer by a low friction medium.
 13. The double-layer supportplatform for positioning patients according to claim 12, wherein saidlow friction medium comprises a plurality of ball transfer units. 14.The double-layer support platform for positioning patients according toclaim 13, wherein said plurality of ball transfer units are mounted on atop side of said bottom layer.
 15. The double-layer support platform forpositioning patients according to claim 14, further comprising aplurality of bearing plates mounted on a bottom side of said top layeropposing said ball transfer units.
 16. The double-layer support platformfor positioning patients according to claim 15, wherein said pluralityof bearing plates are titanium.
 17. The double-layer support platformfor positioning patients according to claim 13, wherein each of saidplurality of ball transfer units comprises a ceramic ball held captivein a non-ferromagnetic housing, said ceramic ball protruding from saidhousing.
 18. The double-layer support platform for positioning patientsaccording to claim 11, wherein a patient's breast to be imaged ispendent through an opening of said pair of openings in said top layerand through a corresponding opening of said pair of openings in saidbottom layer.
 19. The double-layer support platform for positioningpatients according to claim 18, further comprising a removable cover forselectively occluding an opening of said pair of openings in said toplayer.
 20. The double-layer support platform for positioning patientsaccording to claim 11, further comprising a mechanism to constrain arange of motion of said top layer relative to said bottom layer.
 21. Thedouble-layer support platform for positioning patients according toclaim 20, wherein said mechanism to constrain a range of motioncomprises a frame attached to said bottom layer, said top layer beingslidably inserted into the frame.
 22. The double-layer support platformfor positioning patients according to claim 11, further comprising alocking mechanism to selectively lock the top layer in position relativeto the bottom layer.
 23. The double-layer support platform forpositioning patients according to claim 22, wherein said lockingmechanism comprises a friction brake.
 24. The double-layer supportplatform for positioning patients according to claim 23, wherein saidfriction brake is screw-tightened by a knob handle accessible from abovesaid top layer.